A number of problems arise with conventional ink supply systems. The inks that are generally used comprise a pigment and a solvent which tends to evaporate in air, so solvent has to be added continuously during printing. Most conventional systems also utilise a pair of pumps, a first pump being used to pressurise ink and supply it to the printhead, and a second pump being used to pump unused ink away from a gutter system into which uncharged and therefore unutilised droplets are directed. Ink supply systems for conventional printers are frequently complex.